/* Copyright (c) 2011 IETF Trust and the persons identified as */
/* authors of the code. All rights reserved. */
/* See sha.h for terms of use and redistribution. */

/*
* Description:
*	This file implements the Secure Hash Algorithm SHA-1
*	as defined in the U.S. National Institute of Standards
*	and Technology Federal Information Processing Standards
*	Publication (FIPS PUB) 180-3 published in October 2008
*	and formerly defined in its predecessors, FIPS PUB 180-1
*	and FIP PUB 180-2.
*
*	A combined document showing all algorithms is available at
*	http://csrc.nist.gov/publications/fips/fips180-3/fips180-3_final.pdf
*
*	The SHA-1 algorithm produces a 160-bit message digest for a
*	given data stream that can serve as a means of providing a
*	"fingerprint" for a message.
*
* Portability Issues:
*	SHA-1 is defined in terms of 32-bit "words". This code
*	uses <stdint.h> (included via "sha.h") to define 32- and
*	8-bit unsigned integer types. If your C compiler does
*	not support 32-bit unsigned integers, this code is not
*	appropriate.
*
* Caveats:
*	SHA-1 is designed to work with messages less than 2^64 bits
*	long. This implementation uses SHA1Input() to hash the bits
*	that are a multiple of the size of an 8-bit octet, and then
*	optionally uses SHA1FinalBits() to hash the final few bits of
*	the input.
*/

#include "sha.h"

/*
* These definitions are defined in FIPS 180-3, section 4.1.
* Ch() and Maj() are defined identically in sections 4.1.1,
* 4.1.2, and 4.1.3.
*
* The definitions used in FIPS 180-3 are as follows:
*/
#ifndef USE_MODIFIED_MACROS
#define SHA_Ch(x,y,z) (((x) & (y)) ^ ((~(x)) & (z)))
#define SHA_Maj(x,y,z) (((x) & (y)) ^ ((x) & (z)) ^ ((y) & (z)))
#else /* USE_MODIFIED_MACROS */
/*
* The following definitions are equivalent and potentially faster.
*/
#define SHA_Ch(x, y, z) (((x) & ((y) ^ (z))) ^ (z))
#define SHA_Maj(x, y, z) (((x) & ((y) | (z))) | ((y) & (z)))
#endif /* USE_MODIFIED_MACROS */
#define SHA_Parity(x, y, z) ((x) ^ (y) ^ (z))

/*
* Define the SHA1 circular left shift macro
*/
#define SHA1_ROTL(bits,word) (((word) << (bits)) | ((word) >> (32-(bits))))

/*
* Add "length" to the length.
* Set Corrupted when overflow has occurred.
*/
static uint32_t addTemp;
#define SHA1AddLength(context, length) \
		(addTemp = (context)->Length_Low, \
		(context)->Corrupted = \
			(((context)->Length_Low += (length)) < addTemp) && \
			(++(context)->Length_High == 0) ? shaInputTooLong : (context)->Corrupted )

/* Local Function Prototypes */
static void SHA1ProcessMessageBlock(SHA1Context *context);
static void SHA1Finalize(SHA1Context *context, uint8_t Pad_Byte);
static void SHA1PadMessage(SHA1Context *context, uint8_t Pad_Byte);

/*
* SHA1Reset
*
* Description:
*	This function will initialize the SHA1Context in preparation
*	for computing a new SHA1 message digest.
*
* Parameters:
*	context: [in/out]
*		The context to reset.
*
* Returns:
*	sha Error Code.
*
*/
int SHA1Reset(SHA1Context *context)
{
	if (!context) return shaNull;
	context->Length_High = context->Length_Low = 0;
	context->Message_Block_Index = 0;
	/* Initial Hash Values: FIPS 180-3 section 5.3.1 */
	context->Intermediate_Hash[0] = 0x67452301;
	context->Intermediate_Hash[1] = 0xEFCDAB89;
	context->Intermediate_Hash[2] = 0x98BADCFE;
	context->Intermediate_Hash[3] = 0x10325476;
	context->Intermediate_Hash[4] = 0xC3D2E1F0;
	context->Computed = 0;
	context->Corrupted = shaSuccess;
	return shaSuccess;
}

/*
* SHA1Input
*
* Description:
*	This function accepts an array of octets as the next portion
*	of the message.
*
* Parameters:
*	context: [in/out]
*		The SHA context to update.
*	message_array[ ]: [in]
*		An array of octets representing the next portion of
*		the message.
*	length: [in]
*		The length of the message in message_array.
*
* Returns:
*	sha Error Code.
*
*/
int SHA1Input(SHA1Context *context, const uint8_t *message_array, unsigned int length)
{
	if (!context) return shaNull;
	if (!length) return shaSuccess;
	if (!message_array) return shaNull;
	if (context->Computed) return context->Corrupted = shaStateError;
	if (context->Corrupted) return context->Corrupted;
	while (length--) {
		context->Message_Block[context->Message_Block_Index++] =
			*message_array;
		if ((SHA1AddLength(context, 8) == shaSuccess) &&
			(context->Message_Block_Index == SHA1_Message_Block_Size))
			SHA1ProcessMessageBlock(context);
		message_array++;
	}
	return context->Corrupted;
}

/*
* SHA1FinalBits
*
* Description:
*	This function will add in any final bits of the message.
*
* Parameters:
*	context: [in/out]
*		The SHA context to update.
*	message_bits: [in]
*		The final bits of the message, in the upper portion of the
*		byte. (Use 0b###00000 instead of 0b00000### to input the
*		three bits ###.)
*	length: [in]
*		The number of bits in message_bits, between 1 and 7.
*
* Returns:
*	sha Error Code.
*/
int SHA1FinalBits(SHA1Context *context, uint8_t message_bits, unsigned int length)
{
	static uint8_t masks[8] = {
		/* 0 0b00000000 */ 0x00, /* 1 0b10000000 */ 0x80,
		/* 2 0b11000000 */ 0xC0, /* 3 0b11100000 */ 0xE0,
		/* 4 0b11110000 */ 0xF0, /* 5 0b11111000 */ 0xF8,
		/* 6 0b11111100 */ 0xFC, /* 7 0b11111110 */ 0xFE
	};
	static uint8_t markbit[8] = {
		/* 0 0b10000000 */ 0x80, /* 1 0b01000000 */ 0x40,
		/* 2 0b00100000 */ 0x20, /* 3 0b00010000 */ 0x10,
		/* 4 0b00001000 */ 0x08, /* 5 0b00000100 */ 0x04,
		/* 6 0b00000010 */ 0x02, /* 7 0b00000001 */ 0x01
	};
	if (!context) return shaNull;
	if (!length) return shaSuccess;
	if (context->Corrupted) return context->Corrupted;
	if (context->Computed) return context->Corrupted = shaStateError;
	if (length >= 8) return context->Corrupted = shaBadParam;
	SHA1AddLength(context, length);
	SHA1Finalize(context,
		(uint8_t)((message_bits & masks[length]) | markbit[length]));
	return context->Corrupted;
}

/*
* SHA1Result
*
* Description:
*	This function will return the 160-bit message digest
*	into the Message_Digest array provided by the caller.
*	NOTE:
*		The first octet of hash is stored in the element with index 0,
*		the last octet of hash in the element with index 19.
*
* Parameters:
*	context: [in/out]
*		The context to use to calculate the SHA-1 hash.
*	Message_Digest[ ]: [out]
*		Where the digest is returned.
*
* Returns:
*	sha Error Code.
*
*/
int SHA1Result(SHA1Context *context, uint8_t Message_Digest[SHA1HashSize])
{
	int i;
	if (!context) return shaNull;
	if (!Message_Digest) return shaNull;
	if (context->Corrupted) return context->Corrupted;
	if (!context->Computed)
		SHA1Finalize(context, 0x80);
	for (i = 0; i < SHA1HashSize; ++i)
		Message_Digest[i] = (uint8_t)(context->Intermediate_Hash[i >> 2]
			>> (8 * (3 - (i & 0x03))));
	return shaSuccess;
}

/*
* SHA1ProcessMessageBlock
*
* Description:
*	This helper function will process the next 512 bits of the
*	message stored in the Message_Block array.
*
* Parameters:
*	context: [in/out]
*		The SHA context to update.
*
* Returns:
*	Nothing.
*
* Comments:
*	Many of the variable names in this code, especially the
*	single character names, were used because those were the
*	names used in the Secure Hash Standard.
*/
static void SHA1ProcessMessageBlock(SHA1Context *context)
{
	/* Constants defined in FIPS 180-3, section 4.2.1 */
	const uint32_t K[4] = {
		0x5A827999, 0x6ED9EBA1, 0x8F1BBCDC, 0xCA62C1D6
	};
	int t; /* Loop counter */
	uint32_t temp; /* Temporary word value */
	uint32_t W[80]; /* Word sequence */
	uint32_t A, B, C, D, E; /* Word buffers */

	/*
	* Initialize the first 16 words in the array W
	*/
	for (t = 0; t < 16; t++) {
		W[t] = ((uint32_t)context->Message_Block[t * 4]) << 24;
		W[t] |= ((uint32_t)context->Message_Block[t * 4 + 1]) << 16;
		W[t] |= ((uint32_t)context->Message_Block[t * 4 + 2]) << 8;
		W[t] |= ((uint32_t)context->Message_Block[t * 4 + 3]);
	}

	for (t = 16; t < 80; t++)
		W[t] = SHA1_ROTL(1, W[t - 3] ^ W[t - 8] ^ W[t - 14] ^ W[t - 16]);

	A = context->Intermediate_Hash[0];
	B = context->Intermediate_Hash[1];
	C = context->Intermediate_Hash[2];
	D = context->Intermediate_Hash[3];
	E = context->Intermediate_Hash[4];

	for (t = 0; t < 20; t++) {
		temp = SHA1_ROTL(5, A) + SHA_Ch(B, C, D) + E + W[t] + K[0];
		E = D;
		D = C;
		C = SHA1_ROTL(30, B);
		B = A;
		A = temp;
	}

	for (t = 20; t < 40; t++) {
		temp = SHA1_ROTL(5, A) + SHA_Parity(B, C, D) + E + W[t] + K[1];
		E = D;
		D = C;
		C = SHA1_ROTL(30, B);
		B = A;
		A = temp;
	}
	for (t = 40; t < 60; t++) {
		temp = SHA1_ROTL(5, A) + SHA_Maj(B, C, D) + E + W[t] + K[2];
		E = D;
		D = C;
		C = SHA1_ROTL(30, B);
		B = A;
		A = temp;
	}

	for (t = 60; t < 80; t++) {
		temp = SHA1_ROTL(5, A) + SHA_Parity(B, C, D) + E + W[t] + K[3];
		E = D;
		D = C;
		C = SHA1_ROTL(30, B);
		B = A;
		A = temp;
	}

	context->Intermediate_Hash[0] += A;
	context->Intermediate_Hash[1] += B;
	context->Intermediate_Hash[2] += C;
	context->Intermediate_Hash[3] += D;
	context->Intermediate_Hash[4] += E;
	context->Message_Block_Index = 0;
}

/*
* SHA1Finalize
*
* Description:
*	This helper function finishes off the digest calculations.
*
* Parameters:
*	context: [in/out]
*		The SHA context to update.
*	Pad_Byte: [in]
*		The last byte to add to the message block before the 0-padding
*		and length. This will contain the last bits of the message
*		followed by another single bit. If the message was an
*		exact multiple of 8-bits long, Pad_Byte will be 0x80.
*
* Returns:
*	sha Error Code.
*
*/
static void SHA1Finalize(SHA1Context *context, uint8_t Pad_Byte)
{
	int i;
	SHA1PadMessage(context, Pad_Byte);
	/* message may be sensitive, clear it out */
	for (i = 0; i < SHA1_Message_Block_Size; ++i)
		context->Message_Block[i] = 0;
	context->Length_High = 0; /* and clear length */
	context->Length_Low = 0;
	context->Computed = 1;
}

/*
* SHA1PadMessage
*
* Description:
*	According to the standard, the message must be padded to the next
*	even multiple of 512 bits. The first padding bit must be a '1'.
*	The last 64 bits represent the length of the original message.
*	All bits in between should be 0. This helper function will pad
*	the message according to those rules by filling the Message_Block
*	array accordingly. When it returns, it can be assumed that the
*	message digest has been computed.
*
* Parameters:
*	context: [in/out]
*		The context to pad.
*	Pad_Byte: [in]
*		The last byte to add to the message block before the 0-padding
*		and length. This will contain the last bits of the message
*		followed by another single bit. If the message was an
*	exact multiple of 8-bits long, Pad_Byte will be 0x80.
*
* Returns:
*	Nothing.
*/
static void SHA1PadMessage(SHA1Context *context, uint8_t Pad_Byte)
{
	/*
	* Check to see if the current message block is too small to hold
	* the initial padding bits and length. If so, we will pad the
	* block, process it, and then continue padding into a second
	* block.
	*/
	if (context->Message_Block_Index >= (SHA1_Message_Block_Size - 8)) {
		context->Message_Block[context->Message_Block_Index++] = Pad_Byte;
		while (context->Message_Block_Index < SHA1_Message_Block_Size)
			context->Message_Block[context->Message_Block_Index++] = 0;
		SHA1ProcessMessageBlock(context);
	}
	else
		context->Message_Block[context->Message_Block_Index++] = Pad_Byte;

	while (context->Message_Block_Index < (SHA1_Message_Block_Size - 8))
		context->Message_Block[context->Message_Block_Index++] = 0;

	/*
	* Store the message length as the last 8 octets
	*/
	context->Message_Block[56] = (uint8_t)(context->Length_High >> 24);
	context->Message_Block[57] = (uint8_t)(context->Length_High >> 16);
	context->Message_Block[58] = (uint8_t)(context->Length_High >> 8);
	context->Message_Block[59] = (uint8_t)(context->Length_High);
	context->Message_Block[60] = (uint8_t)(context->Length_Low >> 24);
	context->Message_Block[61] = (uint8_t)(context->Length_Low >> 16);
	context->Message_Block[62] = (uint8_t)(context->Length_Low >> 8);
	context->Message_Block[63] = (uint8_t)(context->Length_Low);
	SHA1ProcessMessageBlock(context);
}
